Decaffeination of guaraná seeds in a microextraction column using water-saturated CO2

Experimental data on the reduction of the caffeine content of guaraná seeds with water-saturated supercritical carbon dioxide were obtained in order to provide information on the ability of supercritical fluids for the decaffeination of widely consumed caffeine-rich natural products. The extraction was performed using a semi-continuous flow high-pressure micro-extraction apparatus at 40 and 70 °C and pressures of 100, 200 and 400 bar. Carbon dioxide flow rates of 5.7 and 9.4 g min-1 were used. The extraction curves obtained showed the existence of thermodynamic solubility dependent, intermediate and diffusion controlled regions. Extraction at 400 bar and 70 °C using water-saturated supercritical carbon dioxide at a flow rate of 5.7 g min-1 allowed the removal of almost 98% of the initial caffeine content in wet ground guaraná seeds, in a period of 240 min. When extractions were performed at lower pressures or temperatures, additional time and larger amounts of carbon dioxide were necessary to achieve the same yield. Increasing carbon dioxide flow rate did not present any economic advantage unless the extraction was limited to the thermodynamic solubility region. For total extraction of caffeine, the use of low flow rates resulted in a similar final product yield but at a much lower solvent consumption. A retrograde behavior for the extraction of caffeine from guaraná seeds was also observed at 100 bar for the 40 and 70 °C isotherms.

Subjects

Caffeine

Guaraná seeds

Supercritical extraction

DDC Class

540: Chemie

600: Technik

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Decaffeination of guaraná seeds in a microextraction column using water-saturated CO2